Three-dimensional annuloplasty ring and template

ABSTRACT

An annuloplasty ring having a three-dimensional discontinuous form generally arranged about an axis with two free ends that are axially offset. The ring is particularly suited for repair of the tricuspid valve, and more closely conforms to the annulus shape. The ring is more flexible in bending about radially extending axes than about the central axis. The ring may have an inner structural support covered by a pliable sleeve and/or a fabric tube. The structural support may have a varying cross-section, such as a C-shaped cross-section in a mid-section between two free ends and a rectangular cross-section at the free ends. A deliver template having a mounting ring with about the same shape as the ring facilitates implant, and may be releasably attached to a delivery handle. The deliver template may include a plurality of cutting guides for releasably attaching the annuloplasty ring thereto while presenting maximum outer surface area of the ring. The template may have an outwardly-facing groove to receive and retain the ring.

FIELD OF THE INVENTION

[0001] The present invention relates generally to medical devices andparticularly to a tricuspid annuloplasty ring and delivery template.

BACKGROUND OF THE INVENTION

[0002] In vertebrate animals, the heart is a hollow muscular organhaving four pumping chambers: the left and right atria and the left andright ventricles, each provided with its own one-way valve. The naturalheart valves are identified as the aortic, mitral (or bicuspid),tricuspid and pulmonary, and are each mounted in an annulus comprisingdense fibrous rings attached either directly or indirectly to the atrialand ventricular muscle fibers.

[0003] Heart valve disease is a widespread condition in which one ormore of the valves of the heart fails to function properly. Diseasedheart valves may be categorized as either stenotic, wherein the valvedoes not open sufficiently to allow adequate forward flow of bloodthrough the valve, and/or incompetent, wherein the valve does not closecompletely, causing excessive backward flow of blood through the valvewhen the valve is closed. Valve disease can be severely debilitating andeven fatal if left untreated.

[0004] Various surgical techniques may be used to repair a diseased ordamaged valve. In a valve replacement operation, the damaged leafletsare excised and the annulus sculpted to receive a replacement valve.

[0005] Another less drastic method for treating defective valves isthrough repair or reconstruction, which is typically used on minimallycalcified valves. One repair technique that has been shown to beeffective in treating incompetence is annuloplasty, in which theeffective size of the valve annulus is contracted by attaching aprosthetic annuloplasty repair segment or ring to an interior wall ofthe heart around the valve annulus. The annuloplasty ring is designed tosupport the functional changes that occur during the cardiac cycle:maintaining coaptation and valve integrity to prevent reverse flow whilepermitting good hemodynamics during forward flow. The annuloplasty ringtypically comprises an inner substrate of a metal such as stainless ortitanium, or a flexible material such as silicone rubber or Dacroncordage, covered with a biocompatible fabric or cloth to allow the ringto be sutured to the heart tissue. Annuloplasty rings may be stiff orflexible, may be split or continuous, and may have a variety of shapes,including circular, D-shaped, C-shaped, or kidney-shaped. Examples areseen in U.S. Pat. Nos. 5,041,130, 5,104,407, 5,201,880, 5,258,021,5,607,471 and, 6,187,040 B1. Most annuloplasty rings are formed in aplane, with some D-shaped rings being bowed along their anterior orstraight side to conform to the annulus at that location.

[0006] The present application has particular relevance to the repair oftricuspid valve, which regulates blood flow between the right atrium(RA) and right ventricle (RV), although certain aspects may apply torepair of other of the heart valves.

[0007] The tricuspid valve 20 is seen in plan view in FIG. 1 andincludes an annulus 22 and three leaflets 24 a, 24 b, 24 c (septal,anterior, and posterior, respectively) extending inward into the floworifice defined by the annulus. Chordae tendineae 26 connect theleaflets to papillary muscles located in the RV to control the movementof the leaflets. The tricuspid annulus 22 is an ovoid-shaped fibrousring at the base of the valve that is less prominent than the mitralannulus, but slightly larger in circumference. The septal leaflet 24 ais the site of attachment to the fibrous trigone, the fibrous “skeletal”structure within the heart. The triangle of Koch 30 and tendon of Todaro32 provide anatomic landmarks during tricuspid valve repair procedures.The atrioventricular (AV) node 34 is a section of nodal tissue thatdelays cardiac impulses from the sinoatrial node to allow the atria tocontract and empty their contents first, and relays cardiac impulses tothe atrioventricular bundle. In a normal heart rhythm, the sinoatrialnode generates an electrical impulse that travels through the right andleft atrial muscles producing electrical changes which is represented onthe electrocardiogram (ECG) by the p-wave. The electrical impulse thencontinue to travel through the specialized tissue of the AV node 34,which conducts electricity at a slower pace. This will create a pause(PR interval) before the ventricles are stimulated. Of course, surgeonsmust avoid placing sutures too close to or within the AV node 34.C-rings are good choices for tricuspid valve repairs because they allowsurgeons to position the break in the ring adjacent the AV node 34, thusavoiding the need for suturing at that location.

[0008] Despite numerous designs presently available or proposed in thepast, there is a need for a tricuspid ring that more closely conforms tothe actual shape of the tricuspid annulus.

SUMMARY OF THE INVENTION

[0009] The present invention provides an annuloplasty ring including aring body generally arranged about an axis and being discontinuous so asto define two free ends. The ring body has a relaxed configurationfollowing a three-dimensional path such that the free ends are axiallyoffset from an annulus reference plane through a midpoint of the ringbody. In a preferred embodiment, the two free ends are axially offsetbetween about 2-15 mm. The annuloplasty ring is particularly adapted toreinforce the tricuspid annulus, and as such has a curvilinear anteriorside ending in one of the free ends, a curvilinear posterior side endingin the other of the free ends, and a relatively straight septal sideextending between the anterior and posterior sides. The posterior sideis shorter and has a smaller radius of curvature than the anterior side.

[0010] In accordance with one aspect of the present invention, the ringbody comprises an inner structural support of multiple bands of elasticmaterial. A low friction material may be interposed between each twoadjacent bands to facilitate movement therebetween. The multiple bandsmay be embedded in a matrix of pliable material, preferably moldedsilicone. In one embodiment, there are two concentrically disposed bandsembedded in the matrix of pliable material. To facilitate bending aboutaxes that extend radially, each of the multiple bands of elasticmaterial may have a relatively wider radial dimension than its axialdimension.

[0011] Another aspect of the invention is an annuloplasty ring thatcomprises a three-dimensional ring body generally arranged about acentral axis and being discontinuous so as to define two free ends,wherein the ring body has a construction that renders it more flexiblein bending at the two free ends than in a midpoint thereof.

[0012] The annuloplasty ring body may comprise an inner structuralsupport having two free ends, a curvilinear anterior side ending in oneof the free ends, a relatively straight septal side ending in the otherof the free ends, and a curvilinear posterior side extending between theanterior and septal sides, wherein a majority of the posterior side liesgenerally in a plane perpendicular to the axis. The two free ends aredesirably both axially offset in the same direction from the plane.Also, the structural support may have a cross-section that changesaround its length. For example, the the cross-section may be partlyC-shaped in the posterior side, yet the two free ends are rectangular.

[0013] In accordance with a further aspect of the invention, the ringbody may comprise an inner structural support band surrounded by apliable matrix, wherein the matrix includes a tubular inner portion thatsurrounds the band and an outer flange through which implantationsutures can pass. The outer flange may be curved so as to be convex onits outer surface. Preferably, the outer flange is connected to theinner tubular portion with a plurality of circumferentially spaced apartradial walls so as to create a celled structure.

[0014] A further aspect of the present invention provides anannuloplasty ring including a ring body generally arranged about thecentral axis and being discontinuous so as to define two free ends. Thering body has a construction that renders it more flexible in bendingabout axes that extend radially from the central axis than about thecentral axis itself. The ring body may comprise an inner structuralsupport of multiple bands of elastic material. A low friction materialmay be interposed between each two adjacent bands. The multiple bandsmay be embedded a matrix of pliable material, preferably silicone. Theremay be two concentrically disposed bands embedded in the matrix ofpliable material. Desirably, each of the multiple bands elastic materialhas a relatively wider radial dimension than its axial dimension.

[0015] In a still further aspect of the present invention, anannuloplasty ring template is provided. The template has a rigid bodywith a peripheral mounting ring generally arranged about an axis andbeing discontinuous so as to define two free ends. The mounting ringfollows a three-dimensional path such that the free ends are axiallyoffset. The template may include a central platform to which theperipheral mounting ring is connected via a plurality of generallyradially extending spokes. A handle-receiving hub may extend generallyaway from central platform. Desirably, the peripheral mounting ringextends about three-quarters circumferentially about the axis.

[0016] In a preferred embodiment, the peripheral mounting ring of thetemplate defines a radially outward groove therein for receiving anannuloplasty ring. The template further may include a plurality ofcutting guides provided on the peripheral mounting ring. A pair ofthrough holes in the mounting ring are provided on either side of eachcutting guide such that a length of suture may extend through or aboutan annuloplasty ring positioned on the outside of the mounting ring,through one of the holes, over the cutting guide, through the otherhole, and back into the annuloplasty ring. Each cutting guide maycomprise a pair of intersecting slots, one of the slots being shallowerthan the other and positioned to receive a suture extending between thethrough holes. The deeper slot provides space into which a sharpinstrument may extend to sever the suture at the cutting guide.

[0017] Further understanding of the nature and advantages of theinvention will become apparent by reference to the remaining portions ofthe specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a plan view of the tricuspid valve and surroundinganatomy;

[0019]FIG. 2 is a perspective view of an exemplary annuloplasty ring ofthe present invention illustrating its axially-spaced free ends;

[0020]FIG. 2A is a cross-sectional view of the exemplary annuloplastyring taken along line 2A-2A of FIG. 2;

[0021]FIG. 2B is a cross-sectional view similar to FIG. 2A of anannuloplasty ring of the prior art;

[0022] FIGS. 2C-2E are cross-sectional views of alternative annuloplastyrings of the present invention taken through the rings in the samelocation as line 2A-2A of FIG. 2;

[0023]FIG. 3 is a perspective view of a tricuspid valve and surroundinganatomy;

[0024]FIG. 4 is a plan view of the annuloplasty ring of FIG. 2 implantedaround the tricuspid valve;

[0025]FIG. 5 is a perspective view of exemplary annuloplasty ring,holder template and delivery handle of the present invention;

[0026]FIG. 6 is a perspective view of the ring, template and handlecombination of FIG. 5 positioned above the tricuspid valve and showingan exemplary attachment method;

[0027] FIGS. 7A-7C are perspective and elevational views of a furtherexemplary holder template of the present invention;

[0028] FIGS. 8A-8D are perspective, elevational and plan views of arigid yet elastic inner structural support of an alternativeannuloplasty ring of the present invention; and

[0029] FIGS. 9A-9C are sectional views through the structural support ofFIGS. 8A-8D, taken along the section lines indicated in FIG. 8B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The present invention provides a non-planar or three-dimensional(3D) annuloplasty ring that is shaped to conform to a 3D annulus. Somestudies show that the tricuspid valve has such a non-planar annulus, andthus the present invention is particularly suited for repair of thatvalve. Of course, other valves may in some patients have 3D annuluses,and the annuloplasty ring of the present invention may also have use inthose locations, if desired by the surgeon. Of course, all annuloplastyrings are three-dimensional to some extent, as they have across-sectional thickness. In the context of the present invention, anon-planar or three-dimensional annuloplasty ring has a nominalcross-sectional centerline that assumes a three-dimensional shape, or inother words does not lie in a single plane. Likewise, the exemplary ringof the present invention, as well as other shapes that may benefit fromthe features embodied herein, has a non-circular peripheral shape, butis shown having an axis. The term “axis” in reference to the illustratedring, and other non-circular or non-planar rings, refers the linethrough the ring that passes through the area centroid of the ring whenviewed in plan view. This “axis” can also be viewed as imaginary line ofblood flow within the valve orifice and thus within the ring whenimplanted therein.

[0031] It should be understood that the various constructional detailsof any one embodiment herein may be transferred to another embodiment,even if not explicitly mentioned. For instance, the inner ringstructural support seen in FIGS. 8A-8D may be used in a ring that has asilicone sleeve and outer fabric covering as described elsewhere. Also,the templates 90 or 110 seen in FIGS. 5-7 may be adapted to conform toand hold the ring constructed using the inner ring structural supportseen in FIGS. 8A-8D.

[0032] Despite numerous ring designs in the past, none has effectivelyaccommodated the shape of the tricuspid valve. Prior C-shaped rings(i.e., those with a break in continuity around the periphery) are formedin a plane. When implanted, a planar ring will tend to conform anon-planar annulus to its own shape because of its relative stiffness.Unfortunately, this may interfere with optimum performance of the“repaired” valve.

[0033]FIG. 2 illustrates an exemplary annuloplasty ring 40 of thepresent invention having a ring body 42 generally arranged about an axis44 and being discontinuous so as to define two free ends 46 a, 46 b.FIG. 3 shows a tricuspid valve 20 in perspective, and FIG. 4 shows theannuloplasty ring 40 in plan view after having been implanted orotherwise affixed to the tricuspid valve 20. When viewed in plan view,as seen in FIG. 4, the body 42 of the annuloplasty ring 40 defines arelatively straight septal side 50 a, a curvilinear posterior side 50 b,and a curvilinear anterior side 50 c. The posterior side 50 b is shorterand has a smaller radius of curvature than the anterior side 50 c.

[0034] Again, the axis 44 in FIG. 2 lies at the centroid of the ring oralong of the axis of blood flow through the ring 40 when implanted, andit will be understood that the directions up and down are as viewed inthe figure. The ring 40 is designed to be implanted in a tricuspidannulus such that blood will flow in the downward direction.

[0035]FIG. 2 illustrates an exemplary axial offset of the two free ends46 a, 46 b. Radial lines are shown from each free end 46 a, 46 b to thecentral axis 44. The distance A between the intersections of theseradial lines and the axis 44 represents the axial offset. The distance Amay vary depending on the patient, but is typically between about 2.0 mmand 15.0 mm. In this embodiment, the curvilinear anterior side 50 c liesgenerally in a plane all the way to the free end 46 a. Therefore,because the second free end 46 b drops below the main part of theanterior side 50 c, which generally defines an annulus reference planefor the ring and host annulus, then it is axially offset from the firstfree end 46 a. However, the first free end 46 a may not lie in theannulus reference plane, and may drop to the same elevation as thesecond free end 46 b. Either free end 46 a, 46 b may even be axiallyabove the annulus reference plane. In short, the ring 40 is designed tobe three-dimensional to conform to the native tricuspid annulus, andthose of skill in the art will recognize the number of possiblepermutations.

[0036] Although the annuloplasty ring 40 may be constructed in a numberof ways as defined in the prior art, one particularly usefulconstruction includes some relatively rigid yet elastic inner structuralsupport surrounded by a pliable core material and a fabric cover. Forexample, as seen in FIG. 2A, the annuloplasty ring 40 may include aninner skeleton of multiple bands 60 of relatively rigid yet elasticmaterial such as Elgiloy surrounded by a suture-permeable core material62 such as silicone, and having an outer fabric cover 64. The multiplebands 60 may be separated by plastic or other relatively low frictionmaterial (e.g., TEFLON) so as to be able to more easily flex withrespect to one another. It will be noted by those of skill in the artthat the multiple bands 60, which limit the flexibility of the ring 40,are aligned generally perpendicular to the axis 44 and thus the ring isleast flexible in bending about the axis. Desirably, the ring 40 of thepresent invention is more flexible in bending about axes along radiallines from the central axis 44. That is, for example, the free ends 46a, 46 b are more easily flexed up and down parallel to the axis thantoward or away from one another. There are a number of ways toaccomplish this flexibility orientation, as seen in FIGS. 2C-2E.

[0037] In contrast, FIG. 2B shows a cross-section of a ring 70 of theprior art that has an inner skeleton of multiple bands 72 of relativelyrigid material such as Elgiloy surrounded by a suture-permeable corematerial 74 such as silicone, with an outer fabric cover 76. In suchprior devices, the bands 60 are oriented along or parallel to the axis44, and thus are more flexible in bending about the central axis.

[0038]FIG. 2C shows a cross-section of an alternative ring of thepresent invention having a plurality of inner bands 78 embedded in amore pliable matrix 80 such as silicone. As before, the bands 78 aredesirably more rigid than the matrix 80 and provide structural supportto the annulus when implanted. The bands 78 are thin in the axialdimension, and wide in the radial direction, so as to provide thepreferred flexibility characteristics of the ring of the presentinvention. The bands 78 are shown spaced apart with matrix 80 materialtherebetween to enhance the aforementioned flexibility.

[0039]FIG. 2D illustrates a further embodiment in which there are twoconcentrically disposed structural bands 81 embedded in a matrix 82 ofpliable material. The bands 81 together create the desired flexibilitycharacteristics of the ring, as explained above, even if theirrespective cross-sections are square or circular. As seen, however, thebands 81 preferably have a larger radial than axial dimension whichcontributes to the flexibility of the ring about radial axes.

[0040]FIG. 2E shows a cross-section of a ring having a circularreinforcing band 83 surrounded by a pliable matrix 84. A tubular innerportion of the matrix 84 surrounds the band 83, while an outer wall orflange 85 provides additional material through which implantationsutures can pass. In a preferred embodiment, the flange 85 is curved soas to be convex on its outer surface, and is connected to the innertubular portion with a plurality of circumferentially spaced apartradial walls 86. A series of circumferential cells 87 is thus createdbetween the walls 86. The celled structure of the matrix 84 renders itsoft and compressible, which facilitates conformance of the ring to veryuneven annuluses. A fabric covering (not shown) may also be used.

[0041] With reference again to FIGS. 2 and 3, the three-dimensionalshape of the annuloplasty ring 40 is seen corresponding generally to theshape of the tricuspid annulus 22. The first free end 46 a registerswith an area adjacent the septal leaflet 24 a, to the anterior side ofthe AV node 34. The second free end 46 b registers with an area adjacentthe septal leaflet 24 a, but to the posterior side of the AV node 34.The second free end 46 b is axially offset with respect to the firstfree end 46 a as is the respective anatomical attachment areas.Therefore, the annuloplasty ring 40 closely conforms to the 3-D shape ofthe annulus 22, and minimal distortion of the tissue occurs whenattaching the ring thereto. Furthermore, the oriented flexibility of thering 40 facilitates the 3-D shape matching, between ring and tissuebecause the free ends 46 a, 46 b may be easily flexed with respect toone another along arcs that are generally parallel to the axis 44.

[0042] The annuloplasty ring 40 is seen in FIG. 4 implanted in theannulus 22 using a plurality of sutures 88, although those of skill inthe art will understand that there are other attachment means. Thesutures 88 are evenly distributed around the ring body 42 and tied offto present minimal surface roughness and reduce the chance of thrombiforming thereon. Again, the free ends 46 a, 46 b are shown on eitherside of the AV node 34, which minimizes the risk of damaging thesensitive conduction system.

[0043] A preferred delivery template and method are also provided forthe three-dimensional annuloplasty ring 40 of the present invention.With reference to FIGS. 5 and 6, the ring 40 is shown releasably securedto a template 90 that is in turn held at the distal end of a deliveryhandle 92. The template 90 provides a suturing platform for the ring 40,maintaining its advantageous shape while being implanted. In thisregard, the template 90 includes a peripheral mounting ring 94 generallyarranged about an axis coincident with the axis 44 of the ring 40. Theperipheral mounting ring 94 is discontinuous so as to define two freeends 96 a, 96 b and generally follows a three-dimensional path such thatthe free ends are axially offset. Desirably, the three-dimensional pathof the peripheral mounting ring 94 is the same as that of theannuloplasty ring 40. Sutures (not shown) or other similar expedientreleasably secure the ring 40 to the template 90 to form the assemblyseen in FIG. 5. A hub 98 of the handle 92 may be releasably attached tothe template using sutures or quick-release clips or the like so thatthe handle may be removed during implantation for better visibility ofthe annulus.

[0044]FIG. 6 shows a step in an interrupted suture implant procedure.After exposing the annulus 22, the surgeon secures a plurality ofindividual sutures 100 around the annulus 22 in the locations that thesutures will be arranged around the ring 40. The free ends of eachsuture 100 are then passed through the corresponding positions in thesuture-permeable outer portion of the ring 40, as seen at 102. After allof the sutures 100 have been pre-threaded through the ring 40, thesurgeon manipulates the ring using the handle 92 down the array ofsutures and into position in the annulus 22. The next steps that are notillustrated include severing each suture close to the ring 40 and tyingthem off as seen in FIG. 4. Again, the handle 92 may be detached fromthe template 90 for this operation. Finally, the template 90 is detachedfrom the ring 40 and removed with any attaching sutures from theoperating site.

[0045] FIGS. 7A-7C are several perspective views of an exemplarytemplate 110 for use in implanting the ring 40 of the present invention.The template 110 includes a peripheral mounting ring 112 connected to acentral platform 114 via a plurality of spokes 116. The template 110 maybe constructed of a variety of materials, with a biocompatible plasticbeing preferred. Windows 117 exist between the spokes 116 for greatervisibility of the implant site. A handle-receiving hub 18 projectsupward from the platform 114 and generally defines a central axis 120 ofthe template 110. The mounting ring 112 extends approximatelythree-quarters around the axis 120 and terminates in two axially-spacedfree ends 122 a, 122 b.

[0046] In a preferred embodiment, the mounting ring 112 includes aradially outwardly opening channel or groove 124, which is sized to haveabout the same curvature as the ring 40, and thus snugly retains thering 40 in place around the template 90. The groove 124 is shallow sothat a majority of the ring projects outward therefrom to facilitateexposure to the annulus and attachment thereto.

[0047] A plurality, preferably three, of cutting guides 126 projectsaxially upward from the mounting ring 112 at regular intervals aroundits periphery. The cutting guides 126 each include a first relativelydeep slot 128 and a second shallower slot 130 crossing the first slot.Sutures (not shown) desirably fasten the ring 40 to the template, andextend across the cutting guides 126 for easy severability. A pluralityof passages 132 in the mounting ring 112 opening in the groove 124permit passage of sutures directly from the ring body 42 through themounting ring to the cutting guides 126. As seen best in FIG. 7A, thereare two such passages 132 on either side of each cutting guide 126. Thepassages 132 are desirably straight holes from the upper surface of themounting ring 112 that intersect and thus open to the concave groove124.

[0048] The overall shape of the mounting ring 112 is three-dimensional,as explained above, with the two free ends 122 a, 122 b being axiallyspaced apart. The three-dimensional may be a gentle spiral, or othersimilar shape as dictated by the particular patient, or by arepresentative sample of patients. In the illustrated embodiment, and asbest seen in FIG. 7C, a majority of the mounting ring 112 lies in aplane, with one side that terminates in the second free end 122 b beingformed in a gentle curve or spiral so as to be axially spaced from thefirst free end 122 a. The annuloplasty ring is arranged on the mountingring 112 so that the portion that will lie adjacent the septal leaflet(see 24 a and 50 a in FIG. 4) extends along the spiral segment of themounting ring. In general, it is believed that many patients have arelatively planar tricuspid annulus around the anterior and posteriorsides, but a depressed septal side. The shape of the mounting ring 112thus mimics the presumed anatomical contour, and thus the ring can besewn into place without unduly distorting the annulus.

[0049] FIGS. 8A-8D illustrate an exemplary inner structural support 150for a tricuspid annuloplasty ring of the present invention. Thestructural support 150 is ultimately is covered with one or more outerflexible layers as described above, and therefore the final ring bodyassumes the shape of the support. The structural support 150 may be madeof a relatively rigid material yet elastic material such as Elgiloy.

[0050] When viewed in plan view, as seen in FIG. 8B, the structuralsupport 150 defines a relatively straight septal side 156 a ending inone of the free ends 154 b, a curvilinear posterior side 156 b, and acurvilinear anterior side 156 c ending in the other of the free ends 154a. The posterior side 156 b is between the other two sides. As in theearlier embodiment, the posterior side 156 b is shorter and has asmaller radius of curvature than the anterior side 156 c.

[0051] The structural support 150 is generally arranged about an axis152 and is discontinuous so as to define two free ends 154 a, 154 b. Amajority of the structural support 150 is located generally in anannulus reference plane 151 (see FIG. 8D) perpendicular to the axis 152,and the two free ends 154 a, 154 b curve away from the plane so as to beoffset therefrom. The annulus reference plane 151 is defined as theplane that is perpendicular to the axis 152 at the elevation of thetricuspid annulus. That elevation, in turn, is represented in thedrawings by the midpoint of the anterior side 156 c, or at least themidpoint of the larger cross-section portion thereof (as detailedbelow). FIG. 8C illustrates a midpoint M in the anterior side 56 c thatrepresents the nominal elevation of the host annulus. A perpendicularline to the axis 152 intersects reference point R. The reference planeis thus perpendicular to the axis 52 through point R.

[0052] As seen best in FIG. 8D, the two free ends 154 a, 154 b are thusaxially offset from the reference plane 151 in the same direction, aswell as each other. Of course, the free ends 154 a, 154 b need not beaxially offset from each other as is shown, though the ring will stillbe three-dimensional (that is, the ring is non-planar). For instance,one or both of the free ends 154 a, 154 b may even curve upward abovethe reference plane 151. The particular three-dimensional configurationis modeled to fit the natural shape of a tricuspid annulus, or at leastto approximate that shape as best as possible, and thus those with anunderstanding of the tricuspid annulus will realize that a variety ofshapes are possible.

[0053] With regard to FIGS. 8B and 9A-9C, the cross-sectional shape ofthe structural support 150, at least along most of the anterior side 156c, is designed so as to have more flexible in bending at the free ends154 a, 154 b. FIG. 9A is a cross-section through the anterior side 156 cand shows a generally C-shaped cross-section with an outwardly-facinggroove 160 formed between an upper web 162 and a lower web 164, bothextending from an inner base portion 166. The upper web 162 extendsslightly farther radially outward than the lower web 164.

[0054] The cross-sectional shape of the structural support 150 changesalong its length, from the midpoint M to the free ends 154 a, 154 b. Thetransition between the cross-section at the middle of the anterior side156 c and the cross-sections at the two free ends 154 a, 154 b isgradual, and is reflected in FIGS. 9A-9C. The webs 162, 164 graduallydiminish in radial dimension until all that is left is the rectangularbase portion 166, as seen in FIG. 9C. Because at both free ends 154 a,154 b the radial dimension is smaller than the axial, the ends are moreflexible in bending about the central axis 152. It should be mentionedthat the properties of the inner ring structural support seen in FIGS.8A-8D may be attained with other structures, for example, with themultiple concentric bands as described above.

[0055] While the foregoing is a complete description of the preferredembodiments of the invention, various alternatives, modifications, andequivalents may be used. Moreover, it will be obvious that certain othermodifications may be practiced within the scope of the appended claims.

What is claimed is:
 1. An annuloplasty ring, comprising: a ring bodygenerally arranged about an axis and being discontinuous so as to definetwo free ends, wherein the ring body has a relaxed configurationfollowing a three-dimensional path such that the free ends are axiallyoffset from an annulus reference plane through a midpoint of the ringbody.
 2. The annuloplasty ring as in claim 1, wherein the two free endsare axially offset from each other.
 3. The annuloplasty ring as in claim2, wherein the distance that the two free ends are axially offset fromeach other is between about 2-15 mm.
 4. The annuloplasty ring as inclaim 1, wherein the ring is adapted to reinforce the tricuspid annulusand has a curvilinear anterior side ending in one of the free ends, arelatively straight septal side ending in the other of the free ends,and a curvilinear posterior side extending between the anterior andseptal sides, the posterior side being shorter and having a smallerradius of curvature than the anterior side.
 5. The annuloplasty ring asin claim 1, wherein the ring body comprises an inner structural supportof multiple bands of elastic material.
 6. The annuloplasty ring as inclaim 5, further including a low friction material interposed betweeneach two adjacent bands.
 7. The annuloplasty ring as in claim 5, whereinthe multiple bands are embedded in a matrix of a pliable material. 8.The annuloplasty ring as in claim 7, wherein the pliable material ismolded silicone.
 9. The annuloplasty ring as in claim 8, wherein thereare two concentrically disposed bands embedded in the matrix of pliablematerial.
 10. The annuloplasty ring as in claim 5, wherein each of themultiple bands of elastic material has a relatively wider radialdimension than its axial dimension.
 11. The annuloplasty ring as inclaim 1, wherein the ring body comprises an inner structural supportband surrounded by a pliable matrix, and wherein the matrix includes atubular inner portion that surrounds the band and an outer flangethrough which implantation sutures can pass.
 12. The annuloplasty ringas in claim 11, wherein the outer flange is curved so as to be convex onits outer surface.
 13. The annuloplasty ring as in claim 11, wherein theouter flange is connected to the inner tubular portion with a pluralityof circumferentially spaced apart radial walls so as to create a celledstructure.
 14. The annuloplasty ring as in claim 1, wherein the ringbody comprises an inner structural support having two free ends, acurvilinear anterior side ending in one of the free ends, a relativelystraight septal side ending in the other of the free ends, and acurvilinear posterior side extending between the anterior and septalsides, wherein a majority of the posterior side lies generally in aplane perpendicular to the axis.
 15. The annuloplasty ring as in claim14, wherein the two free ends are both axially offset in the samedirection from the plane.
 16. The annuloplasty ring as in claim 14,wherein the structural support has a cross-section that changes aroundits length.
 17. The annuloplasty ring as in claim 16, wherein thecross-section is partly C-shaped.
 18. The annuloplasty ring as in claim17, wherein the C-shaped part of the cross-section is in the posteriorside, and wherein the two free ends are rectangular.
 19. An annuloplastyring, comprising: a three-dimensional ring body generally arranged abouta central axis and being discontinuous so as to define two free ends,wherein the ring body has a construction that renders it more flexiblein bending at the two free ends than in a midpoint thereof.
 20. Theannuloplasty ring of claim 19, wherein the ring body comprises an innerstructural support covered by a flexible suture-permable outer layer.21. The annuloplasty ring as in claim 20, wherein the outer layer issilicone.
 22. The annuloplasty ring as in claim 21, wherein the innerstructural support comprises two concentrically disposed bands.
 23. Theannuloplasty ring as in claim 19, wherein the ring body comprises aninner structural support having two free ends, a curvilinear anteriorside ending in one of the free ends, a relatively straight septal sideending in the other of the free ends, and a curvilinear posterior sideextending between the anterior and septal sides, wherein a majority ofthe posterior side lies generally in a plane perpendicular to the axis.24. The annuloplasty ring as in claim 19, wherein the two free ends areboth axially offset from an annulus reference plane through a midpointof the ring body.
 25. The annuloplasty ring as in claim 19, wherein thestructural support has a cross-section that changes around its length.26. The annuloplasty ring as in claim 25, wherein the cross-section ispartly C-shaped.
 27. The annuloplasty ring as in claim 26, wherein theC-shaped part of the cross-section is in a midpoint of the ring body,and wherein the two free ends have a cross-section that renders themmore flexible in bending about the axis.
 28. An annuloplasty ringtemplate, comprising: a rigid body having a peripheral mounting ringgenerally arranged about an axis and being discontinuous so as to definetwo free ends, the mounting ring following a three-dimensional path suchthat the free ends are axially offset from an annulus reference planethrough a midpoint of the ring body.
 29. The annuloplasty ring templateof claim 28, wherein the template includes a central platform to whichthe peripheral mounting ring is connected via a plurality of generallyradially extending spokes.
 30. The annuloplasty ring template of claim29, further including a handle-receiving hub extending generally axiallyfrom the central platform.
 31. The annuloplasty ring template of claim28, wherein the peripheral mounting ring extends about three-quarterscircumferentially about the axis.
 32. The annuloplasty ring template ofclaim 28, wherein the peripheral mounting ring defines a radiallyoutwardly opening groove therein for receiving an annuloplasty ring. 33.The annuloplasty ring template of claim 28, further including aplurality of cutting guides provided on the peripheral mounting ring,wherein a pair of through holes in the mounting ring are provided oneither side of each cutting guide such that a length of suture mayextend through an annuloplasty ring positioned on the outside of themounting ring, through one of the holes, over the cutting guide, throughthe other hole, and back into the annuloplasty ring.